In recent years, the virtual machine (also referred to as a VM) system in which a plurality of virtual machines run on a plurality of physical machines (also referred to as PMs) has become used. In such a system, there is a technique called live migration which allows migration of a VM, which is providing a service, running on a PM to another PM almost without stopping the service.
Operations in the live migration will be specifically discussed with reference to FIGS. 22 and 23. FIG. 22 illustrates an example of a conventional live migration. As illustrated in FIG. 22, a server 2201, which is a PM, has a VM management section 2219. A VM 2211 and a VM 2212 are running on the server 2201 under management of the VM management section 2219. A server 2202, which is a PM, has a VM management section 2229. A VM 2221 is running on the server 2202 under management of the VM management section 2229. Operations of the live migration will be discussed in which the VM 2212 running on the server 2201 is migrated via a network 2200 to be a VM 2222 running on the server 2202.
FIG. 23 illustrates an example of operations in a conventional live migration.
In operation S2301, memory data of the source VM 2212 is copied into a memory of the destination VM 2222. Specifically, the server 2201 transfers the memory data of the source VM 2212 to the server 2202 and the server 2202 stores the received data in the memory of the destination VM 2222.
In operation S2302, there has been a change in the memory data of the source VM 2212 while copying in the operation S2301, and expected transfer time of the changed memory data is more than one second, so that the changed memory data of the source VM 2212 is copied into the memory of the destination VM 2222.
In operation S2303, there has been a further change in the memory data of the source VM 2212 while copying in the operation S2302, and expected transfer time of the changed memory data is more than one second, so that the changed memory data of the source VM 2212 is copied into the memory of the destination VM 2222.
In operation S2304, there has been a further change in the memory data of the source VM 2212 while copying in the operation S2303, and expected transfer time of the changed memory data is one second or less, so that the server 2201 terminates the source VM 2212 and the changed memory data of the source VM 2212 is copied into the memory of the destination VM 2222.
In operation S2305, the server 2202 runs the destination VM 2222.
Resources such as a central processing unit (CPU) and network bandwidth are used in the live migration, so that a necessary time from the start to the end of the live migration depends on an amount of memory data to be copied, an available CPU usage rate, network bandwidth, and so on. When a plurality of live migrations are performed together, taking account of competition among the resources and necessary times, a deployment plan that specifies a sequence of live migrations is made in advance, and the live migrations are performed in accordance with the deployment plan.
A related technique is disclosed in Japanese Laid-open Patent Publication No. 2008-217302.